The present invention relates to a microproduct in the fields of chemistry, biochemistry, biotechnology, and biology (hereinafter called “microproduct”), such as a micromechanical switching element, a microoptical product, a microfluid, a microchemical reactor functional element, a capillary model of a blood fluidity measuring device, a microbioreactor, a microwell array chip, a microinjector, or a micro micro resin pipette tip, and its applied product. More particularly, the invention relates to a resin composition suitable for producing the microproduct by injection molding.
A microproduct requiring minute recesses, such as a microwell array chip, is generally made of a silicon single crystal. A minute protrusion/recess pattern is formed by using an etching method.
However, this method suffers from high material cost and long production time.
Moreover, defective products are produced at a high rate so that the testing accuracy may be decreased due to variation in the minute protrusion/recess pattern.
Furthermore, since the microproduct is expensive, it is necessary to wash the microproduct after the test and reuse the washed microproduct. As a result, the testing accuracy may be decreased due to insufficient washing.
In cell-level inspection and analysis, a pipette tip is necessary as a capillary for adsorbing a lymphocyte (diameter: about 10 μm) placed in a specific microwell (microwell diameter: about 10 μm, microwell pitch: 20 μm) of a microwell array chip as shown in a microscope photograph of FIG. 3, and injecting the lymphocyte into another container.
The volume of one lymphocyte is about one picoliter (pl). As the capillary (pipette tip) used for cells having such a minute volume and small diameter or a test solution, a capillary having a volume of several tens of picoliters is necessary. A related-art capillary is described below.
A glass capillary has been used as a nozzle having an inner diameter of about 15 μm which can sample one cell.
However, the glass capillary poses the following problems.
The glass capillary lacks rigidity. This does not pose a problem in manual cell micromanipulation. However, when mechanically sampling a cell at a high speed, the capillary (particularly the nozzle end) swings and does not stand still, so that precise cell sampling work cannot be performed.
Since the glass capillary has insufficient strength, the glass capillary breaks when contacting (colliding with) a cell chip (e.g. microwell array chip) irrespective of the material for the cell chip.
When installing a cell sampling nozzle in a machine and automatically and continuously sampling cells, the hole of the nozzle must be positioned at the center of the nozzle with high accuracy.
However, it is very difficult to shape the glass capillary with high accuracy.
A cell sampling nozzle such as a pipette tip which handles a human biological substance must be carefully disposed of as a medical waste.
However, the glass capillary easily breaks, and the broken capillary is dangerous.
An artificial ruby nozzle has been used as a nozzle having an inner diameter of about 15 μm which can sample one cell.
However, the artificial ruby nozzle poses the following problems.
The artificial ruby nozzle requires manual surface finish work by a skilled worker. Therefore, the artificial ruby nozzle is expensive (50,000 to 100,000 Yen per product) and cannot be mass-produced.
A cell sampling nozzle handles a human biological substance. In order to prevent biohazard or contamination of the sample, it is desirable to supply a sterilized nozzle under aseptic conditions and change the nozzle for each sample. Therefore, it is necessary to develop a nozzle which can be mass-produced at low cost.
A cell sampling nozzle which handles a human biological substance must be carefully disposed of as a medical waste.
The artificial ruby nozzle cannot be disposed of due to high strength, and it is highly dangerous due to the thin tip.
Therefore, if a microproduct can be produced by injection molding, microproducts having specific quality can be mass-produced in a short time, whereby production cost can be reduced. As a result, the microproduct can be disposed of after use so that a decrease in testing accuracy due to insufficient washing does not occur.
Various attempts have been made to utilize the advantage of injection molding.
In related-art technology, when producing a microproduct requiring minute recesses and protrusions, a stamper having a minute protrusion/recess pattern is attached to a mold cavity, and a molten resin is injected at a high temperature and a high pressure. The injected resin is then solidified by cooling and removed. The micromachined features formed on the stamper are transferred to the surface of the resin plate removed.
The stamper used in the related-art technology is a silicon master or an electroformed nickel master. The resin injected is a general thermoplastic resin, i.e. polypropylene, polyethylene, polystyrene, acrylonitrile-styrene copolymer, or high-fluidity polycarbonate.
In order to precisely transfer the deepest portion of the micromachined features of the stamper, a resin having excellent flow properties is generally used, and the temperature and the pressure during injection are set at very high values.
However, the smallest protrusion/recess of the product shape which can be transferred by injection molding is 0.2 to 0.3 mm. It is necessary to use an MI20 (g/10 min) material and set the injection pressure at 200 to 250 MPa.
JP-UM-A-53-35584 discloses a thin tube having an inner diameter of 0.60 to 2.00 mm. At present, a product having an inner diameter of 0.20 mm can be injected.
JP-A-1-143647 discloses a micropipette. However, since the micropipette disclosed in JP-A-1-143647 is made of glass, this micropipette suffers from the above-described technical problems.
Injection molding can provide a product having a specific quality at low cost. However, since injection molding uses a mold, a resin used must have excellent releasability and flow properties, for example.
Moreover, since an expensive silicon stamper easily breaks, if a resin can be injection molded at a low injection pressure, the high mass production capability of injection molding can be utilized by preventing breakage of the silicon stamper.
On the other hand, an electroformed nickel master does not break. However, since the production process is complicated and requires a long time, production cost is very high. This increases cost of the resulting molded product.